非平衡等离子体水处理器的优化设计及性能评价

在正交实验和单因素实验的基础上,对非平衡等离子体水处理反应器的整体结构进行了优化设计,并对优化后反应器的性能进行了定性评价。正交实验结果表明,影响降解效率的因素为气高、液高和气体流量。针高度为4mm、电极间距为17mm、气体流量为96L·h^-1时甲基橙的降解效果最佳。用40目不锈钢网作地电极,采用正脉冲放电能提高降解效率,预处理溶液中放置不锈钢阻挡网有助于提高臭氧的利用率。降解效率和COD去除率随溶液初始浓度的增加而降低,但相同时间内有机污染物的绝对去除量增加,重复实验表明实验误差小于3.5%。     

大气压射频氧气放电特性的数值模拟研究

基于漂移扩散近似,对大气压下氧气射频放电产生的等离子体建立了一维流体模型,包括了电子、正离子和负离子的连续性方程、电子能量方程及泊松方程。采用有限差分法对所建立的模型进行了自洽的数值模拟,得到了相应的数值结果。通过对所得数值结果的分析,研究了大气压下氧气放电的基本特性。研究表明,大气压氧气放电中等离子体密度可达到10¹²cm^-3 ,电子温度约在1.23eV,放电中主要的负离子是O^-离子;随着电压峰值的增加,电子密度、电子温度都增加,但n_O-/n_e 的比率先增加到7.5%又后减小到5%,在电压峰值为700V 时达到最大。     

气压对于低气压双频容性耦合Ar/O2 等离子体放电特性影响的研究

 研究了气压对双射频氩氧混合等离子体电子温度和电子密度的影响。在13.56MHz低频功率和94.92MHz高频功率固定为60W和氩氧气体比为1:9的情况下,利用发射光谱法分析了气压不同时氩氧混合等离子体的放电光谱中的特征谱线的变化规律。使用一维质点网格法(PIC-MC)静电模型计算了电子温度和电子密度。结果表明：电子温度随着气压的增加先降低后升高,与实验结果趋势相吻合;电子密度随着气压的增加先增大后减小。     

微空心阴极放电时空特性

为了揭示微空心阴极放电的放电机理,利用流体模型研究了矩形微空心阴极放电的时间和空间分布特性。在氩气环境下计算得到了压强为1.3×10~4Pa时电流、电势、电场、电子和离子密度等随时间的发展变化。结果表明,整个放电过程分为四个阶段,即预放电阶段、电场由轴向向径向转换阶段、电流缓慢增长向空心阴极效应过渡阶段和稳态放电阶段。稳态放电时出现明显的空心阴极效应,阴极位降区存在很高的径向电场和较高的电子平均能量,而负辉区径向电场很弱,电子平均能量较低,电子和离子密度峰值出现在负辉区,二者数值基本相等,而在阴极位降区离子密度远高于电子密度。     

质子与重离子肿瘤治疗的进展

简要介绍了质子与重离子肿瘤治疗的历史和现状.现在,全世界有质子治疗中心23家,治疗肿瘤患者总数为39 612人;重离子治疗设备有3台,治疗肿瘤患者4 511人（包括He离子治疗2 054例病人）.     

H2对N2直流辉光放电电子行为的影响

通过用Monte Carlo方法模拟N₂-H₂ 混合气体直流辉光放电等离子体快电子行为，从不同H₂浓度的电子能量分布函数，电子密度以及e_f-N₂碰撞率等方面，研究了加H₂对氮辉光放电等离子体过程的影响. 研究结果表明: 随着H₂浓度的升高，电子的平均能量增加, 电子密度及e_f-N₂的各种非弹性碰撞率减小; 但在 关键词： 2-H₂辉光放电')" href="#">N₂-H₂辉光放电 Monte Carlo模拟 2碰撞率')" href="#">e-N₂碰撞率     

单边带调制ROF链路中交叉相位引起的非线性串扰

利用非线性薛定谔方程,推导计算了基于光学单边带调制的光载射频链路中交叉相位调制引起的非线性串扰,建立了新的分析模型,并和抽运探测法进行了比较.该模型可以用来分析不同的ROF链路,特别是波分复用光电上转换链路.得到了单链路和波分复用链路的传输眼图.信道中由交叉相位调制引起的非线性串扰和调制频率,泵浦和探测能量,光纤长度以及信道间隔等有关,通过仿真验证了理论分析.     

大气压双频氦气放电等离子体特性的数值研究

用一维流体模型研究了大气压双频氦气放电等离子体的特性。数值模拟的结果表明,在单、双频放电中,随着应用电压的增加,电子密度和放电电流都增加。相对于单频放电,双频放电中低频源的耦合效应使得放电中的电流以及电子密度降低。随着低频源电压峰值的增加,电子密度降低,离子通量,电子损失能量以及电子吸收能量均降低;但电子温度和电势随着低频源电压峰值的增加而增加。在相同低频源电压下,随着高频源电压的增加离子流非线性增加。     

介质阻挡放电等离子体中OH自由基的光腔衰荡光谱原位诊断

研制了一套等效噪声吸收可达3×10^-9cm^-1的连续波光腔衰荡光谱装置。用该装置对介质阻挡放电等离子体中的OH自由基和水进行了原位定量测量,考察了OH自由基数密度随气压和放电电压以及放电频率的变化情况。实验结果表明,在(2.13~22.0)Χ10³Pa范围内,随着气压增加,OH自由基数密度在气压较低时增加;而在较高气压时由于H₂O的解离吸附作用使得体系中电子密度减小,OH自由基数密度随之减小。随放电电压和放电频率增加介质阻挡放电等离子体中电子密度和电子能量增加而导致OH数密度增加。     

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Based on 1-D fluid Model, numerical simulation was adopted to study the effect of small admixtures of oxygen on the characteristics of argon and oxygen mixture discharge at atmospheric pressure. According to the model equations, the simulation results showed that as the ratio of oxygen to argon increased from 0.1% to 0.6%, the electron density decreased, the density of O? increased, the density of the total negative particles increased, the electron temperature in sheath decreased. Furthermore, with the increase of discharge time, the density of O? increased, the electron density was obviously divided into three stages: the stage of electron growth, the stage of electron reduction and the stage of electron unchanged. When the ratio of oxygen to argon was within the scope of 1%, the electron density decreased rapidly, the oxygen atom density increased quickly. However, when the ratio of oxygen to argon was between 1% and 4%, as the ration of oxygen to argon increased the electron density decreased slowly and the oxygen atom density grew slowly until held the line.     

大气压氩直流微放电光谱研究

微空心阴极放电或微放电是一种能够实现高气压下放电的有效方法。利用不锈钢空心针作阴极,不锈钢网作阳极,进行了大气压氩直流微放电实验研究。测量了大气压氩微放电光谱,发现氩气的发 射谱线主要集中在690～860 nm范围,且全部为氩原子4p—4s的跃迁。实验研究了不同放电电流、气体压强、气体流量与谱线强度之间的关系,发现谱线强度随放电电流、气体流量增加均增加,而谱线强 度随压强变化呈现不同特征：谱线强度随压强的增加先增加后降低,在13.3 kPa时强度最大。此外,选用跃迁波长为763.51和772.42 nm的两条光谱线,利用发射谱线强度比值法测量了氩气微放电等离子 体的电子激发温度。结果显示,其电子激发温度处于2 000～2 800 K之间,且随放电电流的增加而增加,随气体压强和气体流量的增加而降低。     

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Based on diffuse and drift assumption, a 1-D fluid model of atmospheric pressure oxygen RF discharge was developed. The model includes continuity equations for electrons, positive and negative ions, and energy equation, and Poisson equation for eclectic potential. The finite difference method was adopted to solve the model by numerical simulation. The simulation results show that the electron density and electron temperature were 10¹²cm^-3 and 1.23eV, respectively, and the main negative ion was O^- . As the peak of voltage increased, the electron density and electron temperature increased, however, the ratio of O^-/n_e had a maximum value at 700V.     

Effects of oxygen partial pressure on optical properties of NiOX films deposited by reactive DC-magnetron sputtering

The influence of oxygen partial pressure on the optical properties of NiOX thin films deposited by reactive DC-magnetron sputtering from a nickel metal target in a mixture gas of oxygen and argon was presented.With the oxygen ratio increasing, the reflectivity of the as-deposited films decreased, and optical band gap increased. Thermogravimetric analysis (TGA) showed that the decompose temperature of the films was above 250 ℃. After annealed at 400 ℃, only films deposited at 5% O2/Ar ratio showed high opticalcontrast which was about 52%. Scanning electron microscope (SEM) results revealed that the changes ofsurface morphology were responsible for the optical property variations of the films after annealing. Itsthermal stability and high optical contrast before and after annealing made it a good potential write-onceoptical recording medium.     

Measurements of argon metastable density using the tunable diode laser absorption spectroscopy in Ar and Ar/O_2

Densities of Ar metastable states 1s_5 and 1s_3 are measured by using the tunable diode laser absorption spectroscopy(TDLAS) in Ar and Ar/O2 mixture dual-frequency capacitively coupled plasma(DF-CCP). We investigate the effects of high-frequency(HF, 60 MHz) power, low-frequency(LF, 2 MHz) power, and working pressure on the density of Ar metastable states for three different gas components(0%, 5%, and 10% oxygen mixed in argon). The dependence of Ar metastable state density on the oxygen content is also studied at different working pressures. It is found that densities of Ar metastable states in discharges with different gas components exhibit different behaviors as HF power increases. With the increase of HF power, the metastable density increases rapidly at the initial stage, and then tends to be saturated at a higher HF power. With a small fraction(5% or 10%) of oxygen added in argon plasma, a similar change of the Ar metastable density with HF power can be observed, but the metastable density is saturated at a higher HF power than in the pure argon discharge. In the DF-CCP, the metastable density is found to be higher than in a single frequency discharge, and has weak dependence on LF power. As working pressure increases, the metastable state density first increases and then decreases,and the pressure value, at which the density maximum occurs, decreases with oxygen content increasing. Besides, adding a small fraction of oxygen into argon plasma will significantly dwindle the metastable state density as a result of quenching loss by oxygen molecules.     

Fluid model of the positive column in argon‐oxygen direct current glow discharge

The positive column of argon‐oxygen direct current (DC) glow discharge was investigated using a fluid model at pressures of around 410 Pa and discharge currents from 10 to 40 mA. The model was used to study the influence of an oxygen admixture on the properties of argon discharge. The simulated intensity of the electric field strength was compared with measured values at 5% and 100% of oxygen concentration. The one‐dimensional model in a cylindrical tube is based on the drift‐diffusion approximation of particle flux and the mean‐electron‐energy approximation is used to describe the electron interaction. The model takes into account the radial profile of particle concentration, the neutral gas kinetic temperature profile, and interactions with the wall in the cylindrical glass discharge tube. It was shown that 2% of the oxygen admixture causes a significant increase in longitudinal electric field strength and gas heating.     

电激励O2（1△g）发生器的理论模拟研究

 建立了基于分子反应动力学的氧等离子体化学反应模型，该模型包括了电子与氧分子，以及氧原子与氧分子的碰撞反应过程。利用反应动力学理论计算并讨论了电激励O₂(¹△)发生器的放电参数，发现电子能量应小于2.5eV。电子浓度对O₂(¹△)产率的影响不大，当放电压力与气体线流速一定时，存在最佳的电子平均能量。     

Density functional study of oxygen adsorption on the Mg3Nd (0 0 1) surface

The adsorption of oxygen atoms on Mg₃Nd (0 0 1) surface was studied based on density function theory (DFT), in which the exchange-correlation potential was chosen as the generalized gradient approximation (GGA) in the Perdew and Wang (PW91). The most preferred adsorption position was at the top-hollow site. Upon the optimization on top-hollow site with different coverage, it was found that the adsorption energy decreased with oxygen coverage. The density of states analysis showed that obvious charge transfer took place between O atom and the nearest Nd atom and chemical bond formed between O atom and the nearest Nd atom after O adsorption. The result of surface energy as a function of chemical potential change of oxygen indicated the clean Mg₃Nd (0 0 1) surface was easy to adsorb oxygen and form 1.00 ML surface.     

电激励O2（a1Δg）发生器的实验研究

 在纯氧，及氧气和氩气的混合气体情况下，对射频放电产生O₂（a¹Δg）进行了实验研究。射频频率为13.56MHz，额定功率500W，放电压力133.0~399.0Pa， 氧气流量最大为1.4mmol/s， 氩气流量为2.1mmol/s。研究了O₂（a¹Δg）产率随气体流量、放电气压以及混合气体放电条件的变化。O₂（a¹Δg）产率最大值约为17.5%。