Study on the dynamics of two-degree-of-freedom system with variable stiffness magnetic isolator

This paper presents a novel variable stiffness isolator designed by magnetic springs in parallel with linear positive stiffness spring. Firstly, the two-degree-of-freedom vibration system model with variable stiffness magnetic isolator is established. The amplitude frequency characteristic equation of the system is derived based on the multi-harmonic method, and the corresponding curve of the relationship between the amplitude and frequency is given. The influence of the current on the curve is researched. Results showed that there are two pseudo-resonant peaks in the amplitude–frequency curve, and one is in the low frequency band, the other exists in higher frequency band. The first peak does not exhibit the frequency shift, but the second one bends to the natural frequency obviously. With the increasing of the current, the peaks decrease and the backbone curve changes greatly for the second resonant crest. The Lyapunov exponent curve around the resonant frequency is calculated. It is shown that there is chaotic parameter region for the system, and chaos can be controlled with the variable stiffness magnetic vibration isolator according to this research, which is beneficial to the design of nonlinear vibration isolation system

Study of double-potential-well leaf spring system’s chaotic vibration

Chaotic vibration has become increasingly popular in the study of acoustic and vibration engineering. Many engineering designs have taken advantage of the special characteristics of chaos, and deliberately introduced it into the system to improve efficiency. As an important component, leaf springs have long been used in the suspension system of wheeled vehicles. Recent development is considering chaotic vibration in the design of leaf springs to improve the system’s reliability. However, little experimental research has been carried out to investigate the chaos characteristics of leaf springs. Meanwhile, a preliminary study showed that some of the conventional signal processing methods may not be able to successfully identify the chaos features from a leaf spring test rig due to the complexity of the practical signal. Therefore, in this paper, a leaf spring system’s chaotic vibration and relevant signal processing strategy were investigated in theory and experiment. Firstly, the relationship between the amplitude and frequency of the double potential well system is derived with averaging method. The stability is analyzed on the Vander pol plane and the global bifurcation diagram and Lyapunov exponent spectrum are applied to determine the chaotic regime accurately. Numerical simulation was conducted using a finite element method to give an idea of the leaf spring’s natural frequencies where chaotic vibration can be potentially generated. The experimental rig was then designed based on double potential well theory to generate stable and repeatable chaotic vibration, and an experimental study was carried out to investigate the system’s response characteristics under different excitation strengths and frequencies. An improved signal processing method, Wavelet-SG-EEMD (Wavelet, Savitzky-Golay (SG) and Ensemble Empirical Mode Decomposition (EEMD)), was used to reduce noise and beneficial to identify chaotic features of the vibration signal generated by the system. The nonlinear vibration response features of the system were carefully analyzed. Sub-harmonic phenomena, periodic modes and chaotic behavior were discovered during the experiment

Directory of English/Chinese Names of Scholars in Chinese Studies - 海外中国研究学者名录（英中对照）

The Directory of English/Chinese Names of Scholars in Chinese Studies was a by-product of the "Chinese Studies in North America - Research and Resources" project. It provides both the English and the Chinese names of scholars involved in Chinese Studies mainly in North America. The Chinese names for western scholars resulted from an extensive in the relevant literature and on the internet at appropriate sites to find and authenticate the Chinese names used by these scholars. Where we could not find the Chinese name adopted by a scholar, we have transliterated their name into Chinese characters using the standard reference book 英语姓名译名手册. It is hoped that this directory will be useful for people needing to search for the Chinese names used by western scholars, or for the standard transliterations of their names into Chinese characters. Corrections of inaccurate information and addition of new names of Chinese Studies scholars worldwide are welcome. For corrections, comments and updates, please send emails to Haihui Zhang (Librarian for Chinese studies at East Asian Library, University Library System at University of Pittsburgh) at [email protected]

Nonlinear Giant Magnetostrictive Actuator and Its Application in Active Control

The giant magnetostrictive actuator has great use in vibration control, but the linear model cannot fully describe its dynamic characteristics. In this chapter, based on the domain wall theory and piezomagnetic theory, a hysteresis nonlinear model is established to fully describe the actuator dynamic characteristics. In combination with the regularisation method, a sliding mode controller has been designed, and the giant magnetostrictive actuator is also studied in the application of active control. Experimental results show that the hysteresis nonlinear model proposed in the chapter can fully describe the actuator’s dynamic characteristics in a wider frequency band and the active control also has a much better isolation effect than the passive vibration; it can significantly attenuate the external incentives

English/Chinese Comparison Table for Names of Chinese Studies Scholars [ 北美中国研究学者英中姓名对照 ]

English/Chinese Comparison Table for Names of Chinese Studies Scholars was a by-product of the "Chinese Studies in North America - Research and Resources" project. It provides both the English and the Chinese names of scholars involved in Chinese Studies mainly in North America. The Chinese names for western scholars resulted from an extensive in the relevant literature and on the internet at appropriate sites to find and authenticate the Chinese names used by these scholars. Where we could not find the Chinese name adopted by a scholar, we have transliterated their name into Chinese characters using the standard reference book 英语姓名译名手册. It is hoped that this directory will be useful for people needing to search for the Chinese names used by western scholars, or for the standard transliterations of their names into Chinese characters. Corrections of inaccurate information and addition of new names of Chinese Studies scholars world-wide are welcome. For corrections, comments and updates, please send emails to Haihui Zhang (Librarian for Chinese studies at East Asian Library, University Library System at University of Pittsburgh) at [email protected]

Contamination levels assessment of potential toxic metals in road dust deposited in different types of urban environment

A total of 42 samples of road dust were collected along ring road, city centre, city side, and freeway in Urumqi, China. Total concentrations of Cd, Cr, Cu, Ni, Pb, Mn, Be, Co, Zn, and U were determined by using the inductively coupled plasma-mass spectrometry in order to assess and to compare road dust contamination levels of metals among the four roads. The results show that, among the four categories of roads, mean concentrations of Co and U vary little. City centre locations show strong enrichments of Cd, Cu, Pb, and Be. Along the ring road, the highest mean concentrations were found for Cr, Ni, Mn, and Co. However, the highest concentrations of Zn and U were found along the freeway. The cluster analysis shows that three main groups can be distinguished. Every group may be associated with different main sources and concentrations of the metals. The results of contamination assessment reveal that, among all of the potential toxic metals, Cd, Cu, and Zn pollution were obviously heavier with moderate or high contamination indices for most road dust samples, while Cr, Ni, and Pb contamination were lower along the four categories of roads. Compared with the city side, Cd, Cu, Pb, Ni, and Zn contamination were heavier along the ring road, the city centre, and the freeway with high traffic density. Low Pb contamination or no contamination in all the road dust samples may be related to the increasing usage of lead-free petrol

Heavy metal induced ecological risk in the city of Urumqi, NW China

A total of 169 samples of road dust collected in the city of Urumqi, capital of the Xinjiang Uygur Autonomous Region in northwest China, were analyzed by method of inductively coupled plasma-mass spectrometry for 10 elements (i.e., Cd, Cr, Cu, Ni, Pb, Mn, Be, Co, Zn, and U). The possible sources of metals are identified with multivariate analysis such as correlation analysis, principal component analysis, and cluster analysis. Besides, enrichment factors are used to quantitatively evaluate the influences of human activities on heavy metal concentrations. Moreover, the potential ecological risk index is applied to evaluating the ecological risk of heavy metal pollutants. The results indicate that: (1) the concentrations of the heavy metals involved were much higher in urban areas than the background values, except those of Co and U. Mn, U, and Co are mainly of natural origin; Cu, Pb, Zn, and Cr are mainly of traffic sources and are partly of industrial sources; Ni and Be are mainly the results of industrial activities, such as machine shops, firepower plants, tire and rubber factories, cement factories, and textile mills and are partly of the traffic sources; (2) with high "toxic-response" factor and high concentration, Cd has more serious influences on the environment than other heavy metals. Therefore, commercial and industrial areas are usually characterized by higher potential ecological risk when compared with residential areas and new developing urban areas. The results of this study could be helpful for the management of environment in industrial areas

Spatial distribution and contamination assessment of heavy metals in urban road dusts from Urumqi, NW China

This study reports the spatial distribution pattern and degree of heavy metal pollution (Cd, Cr, Cu, Ni, Pb, Mn, Be, Co, Zn and U) in 169 urban road dust samples from urban area of Urumqi city. The spatial distribution pattern shows that Cu, Pb, Cr and Zn have similar patterns of spatial distribution. Their hot-spot areas were mainly associated with main roads where high traffic density was identified. Ni and Mn show similar spatial distributions coinciding with the industrial areas, while the spatial distribution patterns of Co and U show hot-spot areas were mainly located in the sides of the urban area where the road dust was significantly influenced by natural soils. The spatial distributions of Be and Cd were very different from other metals. The geo-accumulation index suggests that road dust in Urumqi city was uncontaminated to moderately contaminated with Cd, Cu, Ni, Pb, Mn, Be, Zn and U. The integrated pollution index shows IPIs of all road dust samples were higher than 1, suggesting that the road dust quality of Urumqi city has clearly been polluted by anthropogenic emission of heavy metals. Moreover, the spatial distribution pattern of IPIs also shows several distribution trends in the studied region. (C) 2009 Elsevier B.V. All rights reserved

Open Mind, Open Access

Open access is a modern notion of resource sharing in the technology era. It began as a bold reaction of the academic community to the rapidly increased cost of scholarly publishing, and it is now an important concept in digitization and digital libraries. It has hanged the way in which scholarly information is disseminated. While the development of electronic resources and digitization in China in recent years provides rich opportunities for scholarly information exchange, open access both as a concept and as a practice, is yet to be accepted. Open access repositories are very limited in number. Open access as a concept was not on the agenda for digital resource development until 2005 and the first open access library and information repository by National Library of China was launched in July 2006. Prior to this, there were very few open access resources available. Most of them were experimental in nature and inoperable with mainstream Internet tools. Not only do these open access resources not carry the same academic value as other scholarly publications, but also they lack support from both information providers and consumers. By looking at the current status of open access resources in China, this paper will examine some of the primary open access resources in China, such as Qiji Wenku (“Miracle Library”). It will raise issues related to open access in China such as scholarly resource sharing; the cooperation among information providers, creators and consumers; the implication of online copyright in a digital environment; and, the promotion of the idea of resource and technology sharing in the global information transition.unpublishe

The Flow Path of Scholarly Information in Chinese Studies - A preliminary Survey Research

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