Friction-induced vibration considering multiple types of nonlinearities

Nonlinear Dynamics - The friction-induced vibration of a novel 5-DoF (degree-of-freedom) mass-on-oscillating-belt model considering multiple types of nonlinearities is studied. The first type of...     

[2]Pseudorotaxanes Based on Naphtho‐21‐crown‐7 and Secondary Dialkylammonium Salts: Remarkably Improved Association Constants Among Four Threaded Structures

This research article is focused on the recognition interaction of a new host naphtho‐21‐crown‐7 and four secondary dialkylammonium salts. In acetone, they can form 1:1 host‐guest complexes which belong to slow‐exchange systems. We also found the differences of binding affinity and binding selectivity between the host and its complementary guest moieties, which could be ascribed to the aromatic π‐π stacking effect and the acidity increase of N‐methylene and ammonium hydrogens due to the increasing electron withdrawing ability from butyl to methoxyphenyl to phenyl to p‐cyanophenyl substituents in the recognition motif.     

A railway track dynamics model based on modal substructuring and a cyclic boundary condition

This article presents a technique for modelling the coupled dynamics of a railway vehicle and the track. The method is especially useful for simulating the dynamics of high speed trains running on nonlinear tracks. The main hypothesis is a cyclic system: an infinite track on which there is an infinite set of identical vehicles spaced at a regular interval of distance. Thus the main problems of the finite-length track models (e.g. the waves that reflect at the end of the track and interact with the vehicle; and the time interval of integration must be shorter than the track length divided by the velocity) are avoided. The flexibility of the method can be observed from the case studies presented in the present work: a vehicle passing over a hanging sleeper, and the vehicle-track dynamics for different ballast compaction cases. The results show the influence of the hanging sleeper gap on the wheel-rail contact forces, and the bending moment at the sleeper for different ballast compaction cases.     

邻菲罗啉聚西佛碱金属配合物的合成及磁性能研究

以5,6-二胺-1,10-菲罗啉与2,6-吡啶二甲酸缩聚合成得到一种新的含邻菲罗啉结构的聚西佛碱,并制备了其相应的与过渡金属离子Ni2+和Fe2+以及稀土离子Nd3+的配合物,通过红外光谱,核磁共振和元素分析等手段对聚合物及其金属配合物的结构进行了表征,并分析和讨论了它们的磁学性能.结果表明,这一类金属配合物在低温区,...     

Shape optimization of coronary artery stent based on a parametric model

The implantation of intravascular stent (IVS) is a kind of coronary angioplasty to restore the blood flow perfusion to the downstream of the heart muscle tissue. The superior mechanical properties of a stent guarantee the successful implantation. This paper intends to improve the mechanical properties of MAC STENT^TM by utilizing optimization theory instead of the conventional trial-and-error approach. In order to achieve this goal, firstly, a reliable procedure of finite element analysis (FEA) is established based on a parametric geometric model. The FEA overcomes the difficulties due to nonlinearities such as elasto-plasticity, large deformation, large strains and contact. It can simulate the stent's deformations during a loading scheme of three phases without any possible failures or irregularities. Secondly, a single objective function, which includes the main mechanical properties of stents, is proposed to replace the initial multi-objective function and then an optimization model is formulated. An optimal design of MAC-J09-3.0 stent is obtained after successful execution of the optimizing process using 41 loops. Its comprehensive mechanical properties are largely improved. It is concluded that the optimization theory is very useful and efficient in the studies of coronary artery stents, although the optimization task encounters many severe difficulties and requires extensive calculation. The result also shows that the single objective function proposed in this paper is practical.     

Thermomechanical response of metallic sandwich tubes with prismatic cores considering active cooling

In this paper, the transient temperature distribution and the thermomechanical response of sandwich tubes with prismatic cores are analyzed considering active cooling. The effective thermal conductivities of prismatic cores with active cooling are derived. By using the effective thermal conductivities, the transient temperature fields of the tubes are predicted and are found to be very close to the results of finite element simulations, which confirms the correctness of the effective thermal conductivity. Based on the high-order sandwich shell theory, the thermal structural responses of sandwich structures are studied and compared with the results of finite element simulations. The reduction of the thermal structural responses as a result of active cooling is studied to demonstrate the advantages of prismatic cellular materials. The design of replacing the solid metal with cellular materials which has the capability of active cooling can reduce the temperature and the thermal structural response of the structure.     

2-(2,3,5-三氮唑偶氮)-1,8-二羟基-3,6-萘二磺酸与铜的显色反应及其应用

研究了新的水溶性显色剂2-(2,3,5-三氮唑偶氮)-1,8-二羟基-3,6-萘二磺酸与铜的显色反应,并利用该显色反应建立了测定铜的新方法。在pH=5.52的HAc-NaAc缓冲液中,该试剂与铜形成蓝绿色稳定络合物,λ_(max)为550.8nm,表观摩尔吸光系数为2.44×10~4L/(mol·cm),铜的浓度在0.0～1.0μg/mL范围内符合比耳定律。其他金属离子共存时,不经预分离也无需加掩蔽剂,可直接测定食品及环境水样中的微量铜,操作简便,结果准确。     

Quantification of glucose diffusion in human lung tissues by using Fourier domain optical coherence tomography

In this study, we report permeability coefficients of 30% glucose diffusion by the optical coherence tomography signal slope (OCTSS) method in four kinds of human lung tissue in vitro: normal lung tissue, benign granulomatosis lung tissue, squamous cell carcinoma and adenocarcinoma tumor. To quantify the permeability coefficient of the agent, the monitored region was 80 μm thickness at a tissue depth of ca 230 μm from the surface. The permeability coefficients of 30% glucose from 10 independent experiments were averaged and found to be (1.35 ± 0.13) × 10(-5) cm s(-1) from the normal lung tissue, (1.78 ± 0.21) × 10(-5) cm s(-1) from the benign granulomatosis lung tissue, (2.88 ± 0.19) × 10(-5) cm s(-1) from the adenocarcinoma tumor and (3.53 ± 0.25) × 10(-5) cm s(-1) from the squamous cell carcinoma, respectively. It could be clearly seen that the permeability coefficients of 30% glucose increase ca 32%, 113% and 162% in the benign granulomatosis, adenocarcinoma tumor and squamous cell carcinoma of human lung tissue compared with that from the normal lung tissue, respectively. Therefore, we inferred from this pilot study that the OCT imaging is a feasible method to distinguish normal and cancer lung tissue.     

反应性高分子抗菌剂的合成及对棉织物的抗菌整理

通过三元共聚将马来酸酐活性基团引入大分子链中,制备了两个系列的反应性高分子抗菌剂poly(DMAEMA-BC/AAm/MAn)和poly(DMAEMA-DB/AAm/MAn),并用FT-IR对合成的反应性高分子抗菌剂进行了结构表征,用酸碱滴定法测定了其酸值,通过平板活菌计数法测定了反应性高分子抗菌剂的抗菌活性,并表征了它们的抗菌活性对抗菌时间与浓度的依赖关系。通过热整理工艺将三元共聚物与棉织物反应,制得抗菌织物。之后,通过改良振荡烧瓶法测定了抗菌整理后棉织物的抗菌效果,并进一步考察了织物抗菌效果的耐洗性。研究结果表明,少量的马来酸酐(单体摩尔比5%)有助于提高共聚单体的反应活性,共聚物中含少量马来酸酐时,抗菌活性增强。用马来酸酐单体摩尔比5～35%的poly(DMAEMA-BC/AAm/MAn)或5～25%的poly(DMAEMA-DB/AAm/MAn)整理的抗菌织物均具有良好的抗菌效果,且前者经过100次水洗,后者经200次水洗后,仍表现良好的抗菌效果。