Axial uniformity diagnosis of coaxial surface wave linear plasma by optical emission spectroscopy

The coaxial surface wave linear plasma with preeminent axial uniformity is developed with the 2.45 GHz microwave generator.By optical emission spectroscopy,parameters of the argon linear plasma with a length over 600 mm are diagnosed under gas pressure of 30 and 50 Pa and different microwave powers.The spectral lines of argon and Hβ(486.1 nm)atoms in excited state are observed for estimating electron excitation temperature and electron density.Spectrum bands in305–310 nm of diatomic OH(Σ-Π+A X22 i)radicals are used to determine the molecule rotational temperature.Finally,the axial uniformity of electron density and electron excitation temperature are analyzed emphatically under various conditions.The results prove the distinct optimization of compensation from dual powers input,which can narrow the uniform coefficient of electron density and electron excitation temperature by around 40%and 22%respectively.With the microwave power increasing,the axial uniformity of both electron density and electron excitation temperature performs better.Nevertheless,the fluctuation of electron density along the axial direction appeared with higher gas pressure.The axial uniformity of coaxial surface wave linear plasma could be controlled by pressure and power for a better utilization in material processing.

窄播时代的政治传播:中国传统媒体的挑战及其应对策略

信息通信技术与新媒体的发展对中国传统媒体的政治传播造成了冲击。现有研究较少对传统媒体应对这一挑战的理论逻辑与政治意义做出统一的阐释。论文从传统媒体的政治传播职能及其现实困境出发,对上述议题进行了分析。本质上,互联网时代中国传统媒体所面临的挑战是当前传播模式“窄播化”与传统媒体政治传播“大众化”要求之间的矛盾所造成的。研究发现,中国传统媒体采取加强其在互联网平台布局的“多平台策略”,以及同时扮演宣传媒体与商业化内容生产者的“双重身份策略”,以应对上述冲击与挑战。通过运用这两种策略,传统媒体扩展了其受众接触的广度,加大了其受众影响的深度,有效促进了政治传播的“再大众化”。两种策略的成功运用,有助于传统媒体适应新的媒介环境并有效履行其政治传播职能。此外,对传统媒体转型的政治逻辑与积极意义的分析,也有利于丰富和拓展中国政治传播实践的理论诠释。

Characteristics of non-thermal AC arcs in multi-arc generator

To obtain large-volume non-thermal arc plasma(NTAP), a multiple NTAP generator with three pairs of electrodes has been developed. The arc plasma characteristics, including dynamic process, spatial distribution, and rotation velocity in the discharge zone, were investigated by high speed photograph and image processing methods. The results showed that the dynamic behaviors and spatial distribution of the arc plasma were strongly related to the electrode configuration.A swirl flow of multi-arc plasma was formed by adjusting the electrode configuration, and a steady luminance area was clearly observed in the center of the discharge zone. Moreover, the size of the luminance area increased by decreasing the gas flow rate. The electrical connection in series could be formed between/among these arc columns with their respective driving power supplies in the multi-arc dynamic evolution process. An approximately periodical process of acceleration and deceleration of the arc rotation velocity was observed in the multi-arc generator with swirl flow configuration. In general, the mean velocity of arc rotation was higher in the multi-arc generator with swirl flow configuration when a pair of electrodes driven by a power supply were opposite to each other rather than adjacent.

Characteristics of DC arcs in a multi-arc generator and their application in the spheroidization of SiO2

We investigate characteristics of multi-arc torches with three pairs of electrodes(three cathodes and three anodes)and their performance on the spheroidization of SiO2 powder.The effect of electrode arrangement,including adjacent pattern(AD pattern,adjacent electrodes powered by one power supply)and opposite pattern(OP pattern,opposite electrodes powered by one power supply),on the dynamics of arc plasma is investigated based on synchronous acquisition of electrical and optical signals.The results show that both the voltage and spatial distribution of each arc of multiple arcs are more stable compared with those of a single arc.The fluctuation of an arc in multiple arcs mainly comes from the small-scale arc-to-arc restrikes among multiple arcs.Moreover,these arc-to-arc restrikes occur more frequently among multiple arc columns in OP pattern than in AD pattern.Moreover,the high-temperature area of the central region of arc chamber in OP pattern is larger than that in AP pattern.For the spheroidization of SiO2 in this multi-arc generator,the spheronization degrees of plasma treated silica in OP pattern are at least 20%higher than those in AD pattern.

重思新家长主义:非洲国家中的发展型家长主义——基于四个非洲国家的比较案例分析

新家长主义是描述非洲国家政治经济运转模式的核心概念,也被认为是非洲政治动荡和经济停滞的主要原因。但许多非洲国家在具备了新家长主义特征的情况下仍取得了良好的发展绩效,这一发展模式既超出了新自由主义的理论预期,也区别于其他区域的发展模式,是一种发展型的新家长主义。通过对科特迪瓦、加纳、博茨瓦纳和卢旺达的比较案例分析,可以验证发展型家长主义国家的核心特征是政治经济精英相复合的精英权力结构。这种复合型精英结构通过削弱国家掠夺动机、降低政策交易成本以及强化政治稳定的方式推进了发展。对发展型家长主义的阐释有利于激活新家长主义理论,反思非洲新自由主义改革模式并重新发现非洲国家的发展模式。