强电离放电产生高浓度臭氧的基础理论与方法研究

论述了介质阻挡强电离放电形成方法及其产生臭氧的等离子反应过程。实现用电场强度、电子能量控制臭氧产生浓度和分解。采用α型Al2O3制成电介质薄层（230um）以及窄放电间隙（110um）的新工艺、新技术、取得折合电场强度E／n大于400Td的强电离放电,电子取得平均能量大于10eV,臭氧浓度达到250g/Nm^3,臭氧产生效率达到200g/kWh。进行实现了臭氧产生装置生产组合模块化、小型化。     

温度对CrIS热红外卫星资料反演臭氧廓线的影响分析

臭氧是地球大气中一种重要的痕量气体,在光化学反应和气候变化中都扮演着非常重要的角色。高光谱红外卫星可以观测到较高垂直分辨率的大气臭氧信息,但是由于热红外受大气温度影响较大,臭氧反演精度会有所下降。为此详细讨论和分析了温度对臭氧吸收光谱和权重函数的敏感性,以及对臭氧反演精度的影响。首先利用逐线积分辐射传输模型LBLRTM,分别模拟计算了六种不同标准大气模式下,1K的随机温度误差对大气透过率和辐射值的影响,发现1 K温度随机误差和臭氧浓度5%～6%的变化引起的辐射值变化量一致。接着利用CRTM辐射传输模型,针对搭载于美国对地观测卫星Suomi NPP(National Polar-orbiting Partnership)平台上的CrIS(Cross-track Infrared Sounder)红外高光谱观测数据,计算了1K的随机温度误差对大气臭氧权重函数的影响,并计算了由1K温度误差所导致的热红外高光谱资料大气臭氧廓线反演误差,结果显示CrIS对于臭氧的敏感区位于10～100 hPa之间,且1 K的温度误差和6%的臭氧浓度变化引起的权重函数变化量相当。最后以CrIS作为实验数据,在最优估计法框架下,通过特征向量统计法获取臭氧廓线的先验知识,并将大气温度廓线和大气臭氧廓线都作为未知量,进行同步迭代反演。将反演结果和配对的世界臭氧紫外数据中心WOUDC的站点数据进行比较,发现在反演中加入大气温度廓线进行同步迭代后,反演结果有显著提高,尤其在平流层与真值几乎一致,最大相对误差不超过20%,在对流层反演结果相对较差,最大相对误差不超过50%,优于欧洲中期天气预报中心ECMWF(European Center for Medium-range Weather Forecasting)臭氧模式数据集ERA-Interim。     

Reactivity of hydrogen peroxide with respect to ozone

Ozone decomposition in pure water, H₂O₂ aqueous solution, and water with ethanol admixture is investigated. It is found that, in the presence of H₂O₂, ozone decomposes significantly faster than in pure water owing to its interaction with H₂O₂. The effective rate constant (k = (0.023 ± 0.002) l/(mol s)) is determined, which is much higher than the overall rate constant of ozone decomposition in water, but much lower than the specific rate of ozone decomposition in water in the presence of common organic admixtures (fulvic acids, ethanol). It is concluded that at the combined use of O₃ and H₂O₂ for the decomposition of organic admixtures in water, the contribution of their interaction with each other is little.     

多次反射池FTIR光谱法的臭氧浓度反演及其相关性分析

同温层臭氧对人类起保护作用,地面臭氧对人类健康是有害的,能够对它进行多途径多方法监测对于了解臭氧分布和变换规律以及控制污染排放有积极作用.文章利用多次反射式怀特池傅里叶变换红外光谱仪测得傅里叶变换红外光谱,使用非线性最小二乘算法对它们进行反演,准确得到了臭氧浓度.将测得的臭氧浓度结果与开放光路紫外差分光谱仪以及热电公的...     

Effect of ozone addition and ozonolysis reaction on the detonation properties of C2H4/O2/Ar mixtures

Ozone is one of the strongest oxidizers and can be used to enhance detonation. Detonation enhancement by ozone addition is usually attributed to the ozone decomposition reaction which produces reactive atomic oxygen and thereby accelerates the chain branching reaction. Recently, ozonolysis reaction has been found to be another mechanism to enhance combustion for unsaturated hydrocarbons at low temperatures. In this study, the effects of ozone addition and ozonolysis reaction on steady detonation structure and transient detonation initiation and propagation processes in C₂H₄/O₂/O₃/Ar mixtures are examined through simulations considering detailed chemistry. Specifically, the homogeneous ignition process, the ZND detonation structure, the transient direct detonation initiation, and pulsating instability of one-dimensional detonation propagation are investigated. It is found that the homogenous ignition process consists of two stages and the first stage is caused by ozonolysis reactions which consume O₃ and produces CH₂O as well as H and OH radicals. The ozonolysis reaction and ozone decomposition reaction can both reduce the induction length though they have little influence on the Chapman–Jouguet (CJ) detonation speed. The supercritical, critical and subcritical regimes for direct detonation initiation are identified by continuously decreasing the initiation energy or changing the amount of ozone addition. It is found that direct detonation initiation becomes easier at larger amount of ozone addition and/or larger reaction progress variable. This is interpreted based on the change of the induction length of the ZND detonation structure. Furthermore, it is demonstrated that the ozonolysis reaction can reduce pulsating instability and make the one-dimensional detonation propagation more stable. This is mainly due to the reduction in activation energy caused by ozone addition and/or ozonolysis reaction. This work shows that both ozone decomposition reaction and ozonolysis reaction can enhance detonation for unsaturated hydrocarbon fuels.     

Oxidation process of Mg films by using high-concentration ozone for magnetic tunnel junctions

Ozone oxidization process of metal Mg film for the barrier formation in magnetic tunnel junctions (MTJs) is investigated. Ozone exposure method is expected to oxidize ultra-thin metal films more mildly than with the plasma oxidization method, since the energy level of atomic oxygen is ∼2 eV lower in the ozone method than in the plasma method. The main results were as follows: (1) In the case of ozone oxidation, the diffusion coefficient of oxygen in the insulator is much smaller than that in plasma oxidation. (2) Mg–O film thickness, which is formed by reaction immediately on the metal Mg surface, is thicker as compared with the Al case. (3) In the ozone oxidation method of metal films with the thickness of more than the film thickness formed by reaction, the oxidation is spontaneously stopped at the interface to the bottom Co–Fe. As a result, we succeeded in inducing a TMR ratio of 25% at room temperature in MTJs with Mg(1.3 nm)–O barrier with wider exposure range than in the plasma case.     

Neural networks for the dimensionality reduction of GOME measurement vector in the estimation of ozone profiles

Dimensionality reduction can be of crucial importance in the application of inversion schemes to atmospheric remote sensing data. In this study the problem of dimensionality reduction in the retrieval of ozone concentration profiles from the radiance measurements provided by the instrument Global Ozone Monitoring Experiment (GOME) on board of ESA satellite ERS-2 is considered. By means of radiative transfer modelling, neural networks and pruning algorithms, a complete procedure has been designed to extract the GOME spectral ranges most crucial for the inversion. The quality of the resulting retrieval algorithm has been evaluated by comparing its performance to that yielded by other schemes and co-located profiles obtained with lidar measurements.     

吸收光谱法测量大气压空气介质阻挡放电的臭氧浓度

臭氧作为一种强氧化剂和杀菌剂,在污染物降解,食品加工,杀菌消毒,医疗卫生等方面有着非常广泛的应用。大气压介质阻挡放电是一种极为高效的产生臭氧的方法,利用平行平板介质阻挡放电装置,采用交流高压激励,产生了大气压空气非平衡态等离子体。通过测量其电压和发光信号,发现在电压的正、负半周期均存在着许多随机的放电脉冲,并且其脉宽均在几十到几百纳秒之间,这表明其机制是流光放电。放电的光学发射谱包含氮分子的第二正带系(C 3Π-B 3Π)和第一正带系(B 3П-A 3П),氮分子离子的第一负带系(B 2Σ-X 2Σ),以及氧原子谱线(715.7和799.5 nm)。由于流光放电在紫外区域(200~300 nm)没有明显的发射谱线,但臭氧在此区域存在吸收峰,因此可以利用此区域的紫外吸收光谱测量放电产生的臭氧浓度。吸收光谱法可以有效的监测其臭氧浓度的变化情况,其优势在于操作简单,对实验环境要求低,可在放电条件下使用,并且可以连续监测臭氧浓度变化。基于此,通过Beer-Lambert定律计算了臭氧浓度随实验参数的变化,结果发现随外加电压幅值和驱动频率的增加,臭氧浓度升高。这些结果对于大气压介质阻挡放电的工业应用具有重要价值。     

Effective ozone generation utilizing a meshed-plate electrode in a dielectric-barrier discharge type ozone generator

A meshed-plate electrode, an alternative to the conventional plate electrode of the dielectric-barrier discharge (DBD) ozone generator, has been studied in order to show the effectiveness of the meshed-plate electrode in improving ozone generation. A DBD ozone generator with mesh electrode is shown to have the following two advantages: First, such a device produces corona at its thin, sharp edges, thereby decreasing corona onset voltage for a given gap spacing. Second, by utilizing the air-voids of the meshed-plate electrode, the dense ozone produced in the small, high temperature gap region of the DBD can escape rapidly to the low temperature region. As a result, decomposition of the ozone can be reduced. In this study, surface discharge, meshed-plate electrode, and conventional DBD ozone generators are studied and compared experimentally. The maximum ozone generation concentration and ozone generation efficiency are obtained with the meshed-plate type electrode.     

Intensified recovery of lipids,proteins, and carbohydrates from wastewater-grown microalgae Desmodesmus sp. by using ultrasound or ozone

This study evaluates the effect of ultrasound and ozone pretreatments for the subsequent recovery of Desmodesmus sp. biocomponents—lipids, proteins, and carbohydrates—using a response surface methodology. Both pretreatments impact on the recovered lipids quality, solvent waste production and extraction time is analysed for process intensification purposes. For ultrasound pretreatment, independent parameters were energy applied (50–200 kWh/kg dry biomass), biomass concentration (25–75 g/L), and ultrasonic intensity (0.32 and 0.53 W/mL). While for ozone pretreatment, independent parameters were ozone concentration (3–9 mg O₃/L), biomass concentration (25–75 g/L), and contact time (5–15 min). In the case of ultrasound pretreatment, recovery yield reached 97 ± 0.4%, 89 ± 3%, and 73 ± 0.6% for proteins, carbohydrates and lipids respectively. Given process required: energy applied of 50 kWh/kg dry biomass, 75 g/L of biomass concentration, 0.32 W/mL of ultrasonic intensity, and 56 min of time process. Ultrasound caused high cell disruption releasing all proteins, thereby obviating downstream processing for its recovery. Ozone pretreatment recovery yield was 85 ± 2%, 48 ± 1.4%, and 25 ± 1.3%, for carbohydrates, lipids and proteins respectively, under the following conditions: 9 mg O₃/L of ozone concentration, 25 g/L of biomass concentration, and 5 min of contact time that depicts an energy consumption of 30.64 kWh/kg dry biomass. It was found that ultrasound and ozone pretreatments intensified the lysis and biocomponents recovery process by reducing solvent consumption by at least 92% and extraction time between 80% and 90% compared with extraction of untreated biomass biocomponents. Both pretreatments improve the composition of the recovered lipids. It was noted that the yield of neutral lipids increased from 28% to 67% for ultrasound pretreatment while for ozone pretreatment from 49% to 63%. The method used for lipid extraction may also have an effect but here it was kept constant.     

Ozone countergradients over wheat

Summary The gradient method for measuring dry deposition of ozone on short vegetation was employed in a field experiment in Italy's Po Valley. Ozone countergradients involving time periods of about two hours were measured in the morning.     

Ozone production in supersonic nozzles

Ozone production during the efflux of oxygen from a supersonic nozzle is studied theoretically and experimentally. The formation kinetics of atomic oxygen in an electrical discharge in the nozzle is analyzed. An experiment is set up using an optimized nozzle with an electrical discharge in its supersonic section. It is shown that the highest ozone content at the nozzle output is attained when the excess concentration of oxygen atoms is produced in the supersonic section of the nozzle. Zh. Tekh. Fiz. 68, 20–26 (November 1998)     

Estimation of the Covariance Matrix in Hierarchical Bayesian Spatio-Temporal Modeling via Dimension Expansion

Ozone concentrations are key indicators of air quality. Modeling ozone concentrations is challenging because they change both spatially and temporally with complicated structures. Missing data bring even more difficulties. One of our interests in this paper is to model ozone concentrations in a region in the presence of missing data. We propose a method without any assumptions on the correlation structure to estimate the covariance matrix through a dimension expansion method for modeling the semivariograms in nonstationary fields based on the estimations from the hierarchical Bayesian spatio-temporal modeling technique (Le and Zidek). Further, we apply an entropy criterion (Jin et al.) based on a predictive model to decide if new stations need to be added. This entropy criterion helps to solve the environmental network design problem. For demonstration, we apply the method to the ozone concentrations at 25 stations in the Pittsburgh region studied. The comparison of the proposed method and the one is provided through leave-one-out cross-validation, which shows that the proposed method is more general and applicable.     

The reinforcement ability of ozone-treated CNFs on mechanical properties of C–epoxy composites

Carbon nanofibers (CNFs) are ozone-treated for different time durations (45 and 90 min). Changes in surface characteristics of CNFs due to ozone treatment were studied with BET surface area analyzer and Raman spectroscopy. Raman spectroscopic studies showed that ozone treatment is imparting enhanced degree of disorder for CNFs. Changes in surface functional groups of CNFs due to ozone treatment were estimated using elemental analysis and thermogravimetric analysis. The influence of ozone-treated CNFs on the mechanical properties of laminated (2D) carbon fiber-reinforced epoxy matrix (CFRP) composites has been studied. Results indicate that ozone-treated CNFs can improve the mechanical properties of CFRPs significantly as compared to untreated CNFs due to enhanced interface compatibility between the ozone-treated CNFs to the matrix. Ozone treatment of CNFs proposed in this study has the potential to overcome the limitations of the conventional methods of generating functional groups.     

心磁信号广义S变换域奇异值分解滤波方法

针对心磁信号工频及背景噪声干扰问题, 提出了广义S变换奇异值分解(singular value decomposition, SVD)滤波方法.在离散S变换基础上, 导出了广义矩阵S变换和逆变换公式. 通过对采样信号进行广义S变换, 调节时频分辨率, 利用SVD分解方法确定有效心磁信 号区域, 实现自适应时频滤波. 实验结果表明, 该方法能有效滤除工频及背景噪声干 扰, 且在较少奇异值个数情况下可获得更好的滤波性能. 关键词： 心磁信号 S变换 奇异值分解 时频滤波     

Horizontally networked carbon nanotubes grown on Au–Fe catalyst nanoparticles

Undoped and doped indium tin oxide (ITO) with different concentrations (2, 4, and 6 mol%) of different dopants (CuO, Cr₂O₃, and ZrO₂) were prepared in the nano-size scale (19–33 nm) using Pechini method. The thermal decomposition of the precursors was studied. The electrical properties of all the prepared samples were investigated. All the investigated systems have higher conductivity than that of ITO. For ITO doped with CuO, as the concentration of CuO increases, the conductivity increases. The highest conductivity was obtained for ITO doped with 6 mol% of CuO. For ITO doped with Cr₂O₃, as the concentration of Cr₂O₃ increases the conductivity increases and above 4 mol% Cr₂O₃ the conductivity decreases. For ITO doped with ZrO₂, as the ZrO₂ concentration increases, the conductivity increases up to 4 mol% of ZrO₂ and then decreases. The band gap was detected for all the investigated systems.     

电荷补偿对Sr2SiO4∶Eu3+材料光谱特性的影响

采用溶胶-凝胶法制备了Sr2SiO4∶Eu3+发光材料.测量了Sr2SiO4∶Eu3+材料的激发与发射光谱,发射光谱主峰位于618 nm处;监测618 nm发射峰时,所得材料的激发光谱主峰分别为320 nm、397 nm、464 nm和518 nm.研究了Sr2SiO4∶Eu3+材料发射峰强度随电荷补偿剂Li+、Na+和K+掺杂浓度的变化情况.结果显示,随电荷补偿剂浓度的增大,材料发射峰强度均表现出先增大后减小的趋势,但不同电荷补偿剂下,材料发射峰强度最大处对应的补偿剂浓度不同,补偿剂Li+、Na+和K+的浓度分别为8 mol%、7.5 mol%和7 mol%.     

基于差分吸收激光雷达的一种新的对流层臭氧浓度反演算法

差分吸收激光雷达探测对流层臭氧浓度时,气溶胶的干扰会造成较大的误差。提出了一种算法,该算法能够同时反演得到对流层臭氧浓度和气溶胶消光系数,减少气溶胶对反演结果的影响。使用实验数据,分析计算了气溶胶雷达比,气溶胶波长指数、标定点气溶胶后向散射比各种变化参数对反演结果的误差。结果表明,1 km以下,各种变化参数造成的反演误差小于8%,1 km以上臭氧浓度误差主要来源于信号和背景噪声,各种参数反演误差小于3%。最后给出了利用该算法得到对流层臭氧浓度和气溶胶的消光系数垂直廓线,并和传统的双波长差分算法反演结果作了比较分析。实验结果表明该算法是可行的,该算法可以减少气溶胶对差分吸收激光雷达测量结果引起的误差。     

Gome ozone profiles retrieved by neural network techniques: A global validation with lidar measurements

Ozone profiles retrieved from Global Ozone Monitoring Experiment (GOME, flying on ERS-2 satellite) spectra from July 1995 to June 2003 by means of 2 independent neural network (NN) schemes have been validated with ozone lidar measurements performed at different stations belonging to the network for the detection of atmospheric composition changes (NDACC). The retrieval and the whole validation have been carried out by using the performances and resources of the European project Enabling Grid for E-sciencE (EGEE) and of a local Grid at the European Space Research Institute of the European Space Agency (ESRIN/ESA). Roughly 1800 collocated profiles have been found, in tropical, mid-latitude and high-latitude regions; for each lidar station the differences between GOME and lidar profiles have been evaluated and the global performance of the proposed NN approaches has been critically discussed. The results indicate the potentialities for obtaining reliable ozone field analysis on global scale, including detailed altitude resolved trend analysis.     

基于同步光解的OH自由基标定方法

OH自由基是大气中最重要的氧化剂,准确测量对流层OH自由基的浓度是厘清我国二次污染形成机理的关键.本文介绍了一种基于同步光解的OH自由基便携式标定方法,使用汞灯的185 nm线辐射处于层流状态下的具有一定水汽浓度的合成空气,光解HO2和O2定量产生确定浓度的OH, HO2自由基和O3.开展了臭氧浓度及廓线分布因子P和氧气吸收截面等影响因素的准确测量,降低该标定方法的不确定度.进一步构建便携式标定装置,建立应用于实际外场标定的OH自由基浓度快速获取方法.开展基于激光诱导荧光技术OH自由基(LIF-OH)探测系统的准确标定测试,准确产生3×10^8-2.8×10^9 cm^-3浓度的OH自由基, LIF-OH探测系统的荧光信号与自由基浓度具有非常好的相关性.在综合外场观测(STORM)的应用中该标定装置的不确定度为13.0%,具有良好的稳定性和准确性,可以用于复杂外场环境下LIF-OH系统的快速标定.