In recent years, energy and environmental issues have become more and more prominent, and electric vehicles powered by lithium-ion battery have shown great potential and advantages in alleviating these issues. Compared with other batteries, lithium-ion batteries have the advantages of high specific energy, high energy density, long endurance, low self-discharge and long shelf life. However, temperature of the battery has become one of the most important parameters to be handled properly for the development and propagation of lithium-ion battery electric vehicles. Both the higher and lower temperature environments will seriously affect the battery capacity and the service life. Under high temperature environment, lithium-ion batteries may produce thermal runaway, resulting in short circuit, combustion, explosion and other safety problems. Lithium dendrites may appear in lithium-ion batteries at low temperature, causing short circuit, failure to start and other operational faults. In this paper, the used thermal management methods of lithium-ion batteries are introduced and their advantages and disadvantages are discussed and compared. At the same time, the prospect of future development is put forward.

The purpose of this study was to examine the prevalence of Internet addiction in a nationally representative sample of Chinese elementary and middle school students and to investigate Internet addiction among Internet users with different usages. The data were from the National Children's Study of China (NCSC) in which 24,013 fourth- to ninth-grade students were recruited from 100 counties in 31 provinces in China. Only 54.2% of the students had accessed the Internet. According to the criteria of Young's Diagnostic Questionnaire (YDQ), an eight-item instrument, the prevalence of Internet addiction in the total sample was 6.3%, and among Internet users was 11.7%. Among the Internet users, males (14.8%) and rural students (12.1%) reported Internet addiction more than females (7.0%) and urban students (10.6%). The percentage of Internet addicts in elementary school students (11.5%) was not significantly lower than the percentage of middle school students (11.9%). There was no statistically significant difference between the four geographical regions (9.6%, 11.5%, 12.3%, 11.1%) characterized by different levels of economy, health, education, and social environment. As the frequency of Internet use and time spent online per week increased, the percentage of Internet addicts increased. When considering the location and purpose of Internet use, the percentage of Internet addicts was highest in adolescents typically surfing in Internet cafes (18.1%) and playing Internet games (22.5%).

No abstract

No abstract

A new improved Kurtogram was proposed in this paper. Instead of Kurtosis, correlated Kurtosis of envelope signal extracted from the wavelet packet node was used as an indicator to determine the optimal frequency band. Correlated Kurtosis helps to determine the fault related impulse signals not affected by other unrelated signal components. Finally, two simulated and three experimental bearing fault cases are used to validate the effectiveness of proposed method and to compare with other similar methods. The results demonstrate it can locate resonant frequency band with a high reliability than two previous developed methods by Lei et al. and Wang et al. especially for the incipient faults under low load.

No abstract

This paper investigates the global stabilization for a class of high-order time-delay nonlinear systems. Compared with the existing references, a distinct characteristic of this paper rests in time-delay entering high-order, low-order, and linear growth parts of system nonlinearities. Based on Lyapunov-Krasovskii theorem and necessary improvement of the adding a power integrator method, a continuous global state-feedback controller is constructed to preserve the equilibrium at the origin and guarantees the global asymptotic stability of the resulting closed-loop system. Finally, a simple example is provided to demonstrate the validness of the proposed approach.

Background: Agrobacterium rhizogenes-mediated (ARM) transformation is a highly efficient technique for generating composite plants composed of transgenic roots and wild-type shoot, providing a powerful tool for studying root biology. The ARM transformation has been established in many plant species, including soybean. However, traditional transformation of soybean, transformation efficiency is low. Additionally, the hairy roots were induced in a medium, and then the generated composite plants were transplanted into another medium for growth. This two-step operation is not only time-consuming, but aggravates contamination risk in the study of plant-microbe interactions. Results: Here, we report a one-step ARM transformation method with higher transformation efficiency for generating composite soybean plants. Both the induction of hairy roots and continuous growth of the composite plants were conducted in a single growth medium. The primary root of a 7-day-old seedling was decapitated with a slanted cut, the residual hypocotyl (maintained 0.7-1 cm apical portion) was inoculated with A. rhizogenes harboring the gene construct of interest. Subsequently, the infected seedling was planted into a pot with wet sterile vermiculite. Almost 100% of the infected seedlings could produce transgenic positive roots 16 days post-inoculation in 7 tested genotypes. Importantly, the transgenic hairy roots in each composite plant are about three times more than those of the traditional ARM transformation, indicating that the one-step method is simpler in operation and higher efficiency in transformation. The reliability of the one-step method was verified by CRISPR/Cas9 system to knockout the soybean Rfg1, which restricts nodulation in Williams 82 (Nod-) by Sinorhizobium fredii USDA193. Furthermore, we applied this method to analyze the function of Arabidopsis YAO promoter in soybean. The activity of YAO promoter was detected in whole roots and stronger in the root tips. We also extended the protocol to tomato. Conclusions: We established a one-step ARM transformation method, which is more convenient in operation and higher efficiency (almost 100%) in transformation for generating composite soybean plants. This method has been validated in promoter functional analysis and rhizobia-legume interactions. We anticipate a broad application of this method to analyze root-related events in tomato and other plant species besides soybean.