汽车非线性悬架研究

阐述了非线性悬架的研究意义,评述了目前非线性悬架研究的热点、难点、存在的问题和研究方法,并根据当前的研究状况提出了进一步的建议和展望。     

矿井通风设计应注意的问题

介绍了矿井通风设计中易被忽视的几个问题。     

A Spectral Element Approximation to Price European Options. II. The Black-Scholes Model with Two Underlying Assets

We develop a Legendre quadrilateral spectral element approximation for the Black-Scholes equation to price European options with two underlying assets. A weak formulation of the equations imposes the boundary conditions naturally along the boundaries where the equation becomes singular. As examples, we apply the method to price European rainbow and basket options. We compare the efficiency for fully implicit and IMEX integration of the equations in time, three iterative solvers and two diagonal preconditioners. Of the choices, we find that GMRES with a fully implicit approximation in time, preconditioned with the mass matrix is the most efficient.     

Inhibiting tribocorrosion damage of Cr/CrxN coatings by multi-layer design

The two-layer and multi-layer Cr/Cr_xN coatings were fabricated on 316 L stainless steel (316 L SS) substrates by the arc ion plating technique. The two-layer Cr/Cr_xN coating was a typical CrN coating with an adhesive Cr layer. And the multi-layer Cr/Cr_xN coating design was in two dimensions. In the first dimension, the multi-layer Cr/Cr_xN coating consisted of alternative Cr/CrN layers with the thickness ratio of 1:5; in the second dimension, the alternative Cr₂N layers with the thickness of 10 nm were inserted in CrN layers. This design was expected to increase transverse interfaces in a smaller scale. The microstructures, mechanical, corrosion and tribocorrosion performances of both Cr/Cr_xN coatings were systematically investigated. The results showed that the special multi-layer design of Cr/Cr_xN coatings improved mechanical, anti-corrosion and anti-tribocorrosion performances. Compared with the two-layer Cr/Cr_xN coating, the reduced tribocorrosion damage of the muti-layer Cr/Cr_xN coating was closely related to the inhibited synergistic effect between electrochemical corrosion and mechanical wear. In conclusion, the multi-layer Cr/Cr_xN coating was more suitable to work as the surface protective coating than the two-layer Cr/Cr_xN coating in seawater.     

Experimental study on permanent deformation characteristics of coarse-grained soil under repeated dynamic loading

Practical assessment of subgrade settlement induced by train operation requires developing suitable models capable of describing permanent deformation characteristics of subgrade filling under repeated dynamic loading. In this paper, repeated load triaxial tests were performed on coarse-grained soil (CGS), and the axial permanent strain of CGS under different confining pressures and dynamic stress amplitudes was analysed. Permanent deformation behaviors of CGS were categorized based on the variation trend of permanent strain rate with accumulated permanent strain and the shakedown theory. A prediction model of permanent deformation considering stress state and number of load cycles was established, and the ranges of parameters for different types of dynamic behaviors were also divided. The results indicated that the variational trend of permanent strain rate with accumulated permanent strain can be used as a basis for classifying dynamic behaviors of CGS. The stress state (confining pressure and dynamic stress amplitude) has significant effects on the permanent strain rate. The accumulative characteristics of permanent deformation of CGS with the number of load cycles can be described by a power function, and the model parameters can reflect the influence of confining pressure and dynamic stress amplitude. The study’s results could help deepen understanding of the permanent deformation characteristics of CGS.

     

重载列车作用下桥墩-桩基竖向动荷载特性试验研究

为探明大轴重、长编组和高密度重载列车作用下桥墩和桩基承台顶的动荷载特性，开展不同车速和轴重条件下的桥墩-桩基体系竖向动荷载响应现场试验。分析桥墩动荷载曲线的时域、频域特征，采用Kolmogorov法对动荷载幅值进行正态性检验，建立列车参数与动荷载频域特征的联系；基于3σ原则对不同敞车作用下的动荷载特征值(均值、均幅值和均峰值)进行统计，结合实测数据建立重载列车作用下的墩顶动力系数计算公式，并提出墩顶和桩基承台顶的荷载谱公式及其参数取值。结果表明：动荷载响应在时域上可分为快速增加，周期波动和快速衰减3个阶段，在频域上服从倍频规律和幅值调制效应，0~5Hz频段激振对动荷载起控制作用；动荷载幅值服从正态分布，动荷载均峰值和振动能量沿墩身衰减明显，动荷载均值和均峰值随轴重增大而增大，均幅值随轴重的增加而减小；建议采用φ=1+0.0045v计算墩顶动力系数，采用三角级数式拟合桥墩荷载谱效果显著。研究成果可为重载列车作用下桩基的长期承载变形性状及环境振动评估的研究提供关键参数和可靠检验样本。     

Thermodynamic behaviors of Cu in interaction with chlorine,sulfur, phosphorus and minerals during sewage sludge co-incineration

Thermodynamic equilibrium calculations were performed to reveal effects of interactions among Cl, S, P and other minerals on Cu migration. Our results showed that HCl(g), SO₂(g) and (P₂O₅)₂(g) were released from the sewage sludge co-incineration. Cl was found to weaken adsorption of Cu by Al₂O₃, CaO and Fe₂O₃, while S delayed reactions of Fe₂O₃ and Al₂O₃ with Cu, with P having no effect on reactions between the minerals and Cu. Among the coupled systems of Cl, S and P, the co-existences of Cl and S, and Cl, S and P were determined to inhibit Cu volatilization, and the co-existence of Cl and P had an enhancing effect. Cu migration was affected only by S in the S and P system. With the SiO₂, CaO and Al₂O₃ system, both Cl alone and Cl and P led to failed reactions between the minerals and Cu. In the systems of S, S and Cl, S and P, and S, Cl and P, the migration behavior of Cu was mainly affected by S at low temperatures and by Cl at high temperatures, whereas P had no effect on Cu migration during the entire process.     

预应力锚索桩板墙变形特性研究

为了掌握预应力锚索桩板墙的变形规律,查明其影响变形的参数,通过现场实测与数值计算方法对预应力锚索桩板墙的变形进行了研究。实测结果表明,预应力锚索桩板墙在施工阶段最大变形发生在墙的中部,施工完成后,由于锚索的预应力损失、岩土体蠕变以及车辆荷载的作用等原因,变形最大位置逐渐转移到了墙的上部;计算结果表明,墙后填料强度、墙背粗糙度、桩板的柔度、锚索预应力和位置等都对挡墙的水平位移影响显著。为控制挡墙的最大变形,在填料选择方面,要采用变形模量较大,摩擦角较大的填料进行填筑,填料摩擦角以不能低于20°为宜;在桩板的选择方面,要保证桩板粗糙度较大,桩板柔度较小的桩体,桩板的柔度系数宜控制在0.25～0.5范围内;在锚索预应力的大小与作用点位置选择方面,锚索预应力不宜超过600 kN,单排锚索宜作用在0.2H～0.3H高度位置。     

Solitary Multiphonon Bound States and Periodic Wave Solutionin Inharmonic Molecular Crystals

Employing the coherent state ansatz and the time-dependent variational principle, we obtain a partial differential equation of motion from Hamiltonian in inharmonic molecuIar crystals. By using the method of multiple scales. we reduce this equation into the envelope function and find that the amplitude function satisfied a nonlinear Schrodinger equation. Introducing the inverse scattering transformation, we gain the single-, twry and N- soliton solutions. The energy and the spatial configurations of the system are given. We also acquire the periodic wave solution and analyze its stability.