A two-dimensional air streamer discharge modified model based on artificial stability term under non-uniform electric field at low temperature and sub-atmospheric pressure

In this paper, an improved air discharge fluid model under non-uniform electric field is constructed based on the plasma module COMSOL Multiphysics with artificial stability term, and the boundary conditions developed in the previous paper are applied to the calculation of photoionization rate. Based on the modified model, the characteristics of low temperature subatmospheric air discharge under 13 kV direct current voltage are discussed, including needle-plate and needle-needle electrode structures. Firstly, in order to verify the reliability of the model, a numerical example and an experimental verification were carried out for the modified model respectively. Both verification results show that the model can ensure the accuracy and repeatability of the calculation. Secondly, according to the calculation results of the modified model, under the same voltage and spacing, the reduced electric field under low temperature subatmosphere pressure is larger than that under normal temperature and atmospheric pressure. The high electric field leads to the air discharge at low temperature and sub atmospheric pressure entering the streamer initiation stage earlier, and has a faster propagation speed in the streamer development stage, which shortens the overall discharge time. Finally, the discharge characteristics of the two electrode structures are compared, and it is found that the biggest difference between them is that there is a pre-ionization region near the cathode in the needle-needle electrode structure. When the pre-ionization level reaches 1013 cm-3, the propagation speed of the positive streamer remains unchanged throughout the discharge process, and is no longer affected by the negative streamer. The peak value of electric field decreases with the increase of pre-ionization level, and tends to be constant during streamer propagation. Based on the previous paper, this paper constructs the air discharge model under non-uniform electric field, complements with the previous paper, and forms a relatively complete set of air discharge simulation system under low temperature and sub atmospheric pressure, which provides a certain reference for future research.

Polymer Surface Treatment by Atmospheric Pressure Low Temperature Surface Discharge Plasma:Its Characteristics and Comparison with Low Pressure Oxygen Plasma Treatment

The polymer treatment with a low-temperature plasma jet generated on the atmospheric pressure surface discharge （SD） plasma is performed. The change of the surface property over time, in comparison with low pressure oxygen （O2） plasma treatment, is examined. As one compares the treatment by atmospheric pressure plasma to that by the low pressure O2 plasma of PS （polystyrene） the treatment effects were almost in complete agreement. However, when the atmospheric pressure plasma was used for PP（polypropylene）, it produced remarkable hydrophilic effects.

Spectral Diagnosis of Gas Temperature of Atmospheric Pressure Plasma Jet in Helium

For atmospheric pressure plasma jets(APPJ),the gas temperature is essential for their applications.A spectral diagnosis of APPJ’s gas temperature is conducted in this work.The optical emission spectra of helium APPJ are captured by using an optical spectrometer system.Then,the grating secondary spectrum of OH(A2∑+(ν=0)→X2П(ν=0))are used to diagnose the gas temperature of plasmas because the spectrum has excellent resolution.Meanwhile,the vibrational temperatures are estimated by using the vibration sequence of N2band(SPS,the second positive system).On the basis of the method,some important conclusions were obtained.First,the spectral identifying indicates that the grating primary spectrum covers a whole wavelength range from 200 nm to 900 nm,and that the grating secondary spectrum overlaps with the primary spectrum from 400 nm to 900 nm.Second,the gas temperature(about 320 K)is close to the room temperature,while the vibrational temperature of the N2(SPS)is about 5 000 K.The trend of the two temperatures changing with the applied voltage is discussed in the end.

Characteristics of Low Power CH_4/Air Atmospheric Pressure Plasma Jet

A low power atmospheric pressure plasma jet driven by a 24 kHz AC power source and operated with a CH4/air gas mixture has been investigated by optical emission spectrometer. The plasma parameters including the electron excitation temperature, vibrational temperature and rotational temperature of the plasma jet at different discharge powers are diagnosed based on the assumption that the kinetic energy of the species obeys the Boltzmann distribution. The electron density at different power is also investigated by HS Stark broadening. The results show that the plasma source works under non-equilibrium conditions. It is also found that the vibrational temperature and rotational temperat;ure increase with discharge power, whereas the electron excitation temperature seems to have a downward trend. The electron density increases from 0.8×10^21 m^-3 to 1.1×10^21 m^-3 when the discharge power increases from 53 W to 94 W.

Observation of the Emission Spectra of an Atmospheric Pressure Radio-frequency Plasma Jet

An atmospheric pressure plasma jet （APPJ） using radio-frequency （13.56 MHz） power has been developed to produce homogeneous glow discharge at low temperature. With optical emission spectroscopy, we observed the excited species （atomic helium, atomic oxygen and metastable oxygen） generated in this APPJ and their dependence on gas composition ratio and RF power. O and O2（b1∑g^＋） are found in the effluent outside the jet by measuring the emission spectra of effluent perpendicular to the jet. An interesting phenomenon is found that there is an abnormal increase of O emission intensity （777.4 nm） between 10 mm and 40 mm away from the nozzle. This observation result is very helpful in practical operation.

Comparison of electrochemical properties of atmospheric pressure plasma coatings for Al_2O_3-3TiO_2 and CoNiCrAlY in sea water

To improve the durability of underwater rotating products,the corrosion characteristics in harsh marine environment were evaluated through various electrochemical experiments on the Al2O3-3TiO2 and CoNiCrAlY coating layers by atmospheric pressure plasma spray coating process.By evaluating the corrosion resistance of these materials,their applicability to environmentally friendly power generation equipment such as blades of tidal current turbines was examined.According to the Tafel analysis for micro-areas including the coating layer,the coating/metal interlayer and the base metal,the Al2O3-3TiO2 coating layer and the CoNiCrAlY coating layer show markedly lower corrosion current density than the base metal.The corrosion current density of the CoNiCrAlY coating layer (9.75316×10-8A/cm2) is about 1.6 times more than that of the Al2O3-3TiO2 coating layer (6.13139×10-8A/cm2).

Atmospheric Pressure Plasma Jet in Ar and O_2/Ar Mixtures:Properties and High Performance for Surface Cleaning

An atmospheric pressure plasma jet generated in Ar and O2/Ar mixtures has been investigated by specially designed equipment with double power electrodes at 20~32 kHz, and their effects on the cleaning of surfaces have been studied. Properties of the jet discharge are studied by electrical diagnostics, including the waveform of discharge voltage, discharge current and the Q-V Lissajous figures. The optical emission spectroscopy is used to measure the plasma parameters, such as the excitation temperature and the gas temperature. It is found that the consumed power and the excitation temperature increase with increase of the discharge frequency. On the other hand, at the same discharge frequency, these parameters in O2/Ar mixture plasma are found to be much larger. The effect on surface cleaning is studied from the changes in the contact angle. For Ar plasma jet, the contact angle decreases with increase of the discharge frequency. For O2/Ar mixture plasma jet, the contact angle decreases with increase of discharge frequency up to 26 kHz, however, further increase of discharge frequency does not show further decrease in the contact angle. At the same discharge frequency, the contact angle after O2/Ar mixture plasma cleaning is found to be much lower compared to the case of pure Ar. From the results of quadrupole mass-spectrum analysis, we can identify more fragment molecules of CO and H2O in the emitted gases after O2/Ar plasma jet treatment compared with Ar plasma jet treatment, which are produced by the decomposition of surface organic contaminants during the cleaning process.

Comparison between Theoretical and Experimental Radial Electron Temperature Profiles in a Low Density Weakly Ionized Plasma

Experimental and theoretical studies of the radial distribution function of the electron temperature (RDFT) in a low-density plasma and weakly ionized gas for the abnormal glow region are presented. Experimentally, the electron temperatures and densities are measured by a Langmuir probe moved radially from the center to the edge of the cathode electrode for helium gas at different pressures in the low-pressure glow discharge. The comparison of the final experimental data for the radial distribution of electron temperatures and densities for different low pressures ranging from 0.2 to 1.2 torr, with the final proved equation of RDFT confirms that the electron temperatures decrease with increasing product of radial distance and gas pressures, showing a radial decrement dependence of the electron temperature from the center to the edge of the electrode. This is attributed to the increase of the number of electron-atom collisions at higher gas pressures and consequently of the rate of ionization. For the axial distance (L) from the tip of the probe to cathode electrode and the cathode electrode radius (R), a theoretical and experimental comparison for the two conditions L R and L > R, for both cases the produced plasma temperatures decrease and densities increase. It is concluded that the RDFT accurately shows a dramatic decrease for L R by 60% less than RDFT values for L > R similar as for conditions of magnetized and unmagnetized effect for DC plasma. This means that the rate of plasma loss by diffusion decreased for L R, agrees well with the applied of magnetic field

温度和湿度对P-CNT自感知混凝土压敏性的影响

为研究温度与湿度对自感知混凝土(SSC)感知性能的影响,通过低温等离子体改性处理技术对碳纳米管(CNT)进行官能团嫁接,使其在水性体系下获得较好的分散性,并将改性后的CNT(P-CNT)加入混凝土中制备P-CNT/SSC传感器,通过改变含水率与温度条件研究P-CNT/SSC传感器的极化效应与循环加载下的自感知性能。试验结果表明:过高或过低的含水率均不利于SSC的感知性能,其中变化最为明显的是饱水状态下的P-CNT/SSC传感器,其应力敏感系数下降89.8%,并且压敏曲线极不稳定;在变温试验中,P-CNT/SSC传感器的电阻率与温度之间呈现负相关性,高温和低温下的应力敏感系数相较于常温组试件,分别下降了约35.66%和44.53%,并且压敏曲线整体出现了上移或下滑的趋势;P-CNT/SSC传感器在工程应用中的最佳测试环境为常温、自然含水率。

Electrochemical synthesis of ammonia using a cell with a Nafion membrane and SmFe_(0.7)Cu_(0.3-x)Ni_xO_3(x=0―0.3) cathode at atmospheric pressure and lower temperature

Samaria-doped ceria Ce0.8Sm0.2O2-δ(SDC) and SmFe0.7Cu0.3-xNixO3 have been synthesized by the sol-gel method and characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM) and scanning electron microscopy(SEM).The electrochemical synthesis of ammonia was investigated at atmospheric pressure and low temperature,using the SFCN materials as the cathode,a Nafion membrane as the electrolyte,nickel-doped SDC(Ni-SDC) as the anode and silver-platinum paste as the current collector.Ammonia was synthesized from 25 to 100℃ when the SFCN materials were used as cathode,with SmFe0.7Cu0.1Ni0.2O3 giving the highest rates of ammonia formation.The maximum rate of evolution of ammonia was 1.13 × 10-8 mol·cm-2·s-1 at 80℃,and the current efficiency reached as high as 90.4%.

ARTP-ALE Optimized Selection of Low Acetaldehyde Producing Brewer's Yeast and Fermentation Validation

Higher levels of acetaldehyde in beer are one of the major concerns in the current beer industry.Yeast produces acetaldehyde during alcoholic fermentation,and its modification significantly affects beer flavor and quality.A different mutant strain with lower acetaldehyde production and improved ethanol tolerance was constructed using the ARTP-ALE mutagenesis strategy with 4-methylpyrazole-disulfiram.As a result of the mutation,the alcohol dehydrogenase activity of the mutant strain decreased to about 71.22%of that of the wild-type strain.At the same time,the fermentation properties and genetic stability of the newly screened strain showed slight differences from the wild-type strain,and there were no safety concerns regarding industrial use of the mutant strain.

Apparent quantum yield of photosynthesis of winter wheat and its response to temperature and intercellular CO_2 concentration under low atmospheric pressure on Tibetan Plateau

The Tibetan Plateau is characterized by lower atmospheric pressure, lower air temperature and high daily and seasonal variation due to high elevation. The photosynthesis of plants is significantly influenced by these alpine environmental factors. Apparent quantum yield (αA) is one of the basic parameters of photosynthesis and mass production. Its accuracy determination is of significance to model photosynthesis of C3 plants and global change on the plateau. In the Lhasa Plateau Ecological Station with 65.4 kPa of atmospheric pressure at an elevation of 3688 m, Li-Cor 6400 portable photosynthesis system was used to measure light response curves of winter wheat in different temperatures and intercellular CO2 concentration (Ci).The slope of light response curve in weak light area of PFD from 0 to 150 μmol m-2 S-1 was used to evaluate the value of αA. The dependence of αA on temperature and intercellular concentration was analyzed. In 30℃, the average value of αAWaS 0.0476 ± 0.0038. It is not quite different from the values in low elevation areas. αA is influenced both by temperature and by the ratio of CO2and O2 partial pressure ([CO2]/[O2]). The measured values in the previous study were much lower.This might be due to systematic errors from instrument and data processing methods. The values of αA decreased linearly with temperature. It decreased 0.0007 in every 1℃ increase of temperature. The decrease slope is similar to those of C3 plants in the previous researches. While [O2] is constant, αA increases with Ciwith a hyperbolic relationship. In comparison with low elevation areas, the αA on the Tibetan Plateau is more sensitive to increase of CO2.

UV-ARTP复合诱变选育高产纤维素酶菌株

该研究以拟康氏木霉(Trichoderma pseudokoningii)TP-89为出发菌株,利用紫外(UV)和常压室温等离子体(ARTP)复合诱变方法对其进行诱变,并对其遗传稳定进行测定,以期筛选高产纤维素酶且稳定遗传的突变菌株。结果表明,出发菌株TP-89通过UV诱变100 s,ARTP诱变120 s后,筛选出一株纤维素酶产量高且稳定遗传的正突变菌株UA-67,其在产酶培养基上培养4 d时,滤纸酶活为2.59 U/mL、内切酶活为4.26 U/mL、外切酶活为7.79 U/mL,较出发菌株TP-89分别提高85.0%、125.4%和70.1%。

3种灭菌方式对磁外科器件磁通量的影响及灭菌成本分析

目的 分析压力蒸汽、低温等离子及环氧乙烷3种灭菌方式对磁外科器件磁通量的影响及其灭菌成本。方法234件不同规格型号磁外科器件-磁环,配对编号标记后随机分为A组、B组和C组,每组78件(39对),其中A组使用压力蒸汽灭菌,B组使用低温等离子灭菌,C组使用环氧乙烷灭菌,每对器件按灭菌规范进行包装;测量3组磁环灭菌前后磁通量,对单包灭菌成本和灭菌时间比较分析。结果 3种灭菌方式对磁外科器件磁通量的影响差异无统计学意义(P>0.05),每种灭菌方式灭菌前后的磁通量有统计学差异(P<0.001);灭菌成本:A组为(1.96±0.16)元,B组(23.17±0.32)元、C组(8.16±0.18)元,差异有统计学意义(P<0.01);灭菌时间:A组为(65.21±3.36)min, B组(45.46±1.39)min, C组(1 020.38±12.21)min,差异具有统计学意义(P<0.01)。结论 3种灭菌方式对磁外科器件的磁通量没有影响。压力蒸汽灭菌法单包成本最低,低温等离子单包灭菌成本最高,环氧乙烷灭菌时间最长。压力蒸汽应为磁外科手术器件的首选灭菌方法。

低压烧结温度对一步法制备超细晶WC-Co基硬质合金组织及性能的影响

采用等离子球磨技术制得W-C-10Co-0.9VC-0.3Cr_3C_2纳米复合粉体,并利用单向模压成型法将其压制成生坯,再经低压烧结一步法制备成硬质合金。研究表明,等离子球磨3h所获得的复合粉体呈片层状形貌,并且成分分布均匀。在1 380℃及1 400℃烧结时,由于等离子球磨的特殊作用,VC、Cr_3C_2对WC晶粒长大抑制作用突显。1 380℃烧结制备的硬质合金,致密度为99.2%,WC平均晶粒尺寸为250nm,硬度和横向断裂强度分别为92.3HRA和2 443 MPa,具有最佳的WC晶粒尺寸与致密度配合,以及最佳的综合力学性能。

多针-平板电极介质阻挡放电的研究

通过电压 电流波形图和电压 电荷李萨育图形的测量 ,研究了空气中多针 平板电极介质阻挡放电的特性 ,比较了这种放电和平板 平板电极介质阻挡放电的区别。并通过接触角测量 ,比较了这两种形式放电对聚四氟乙烯进行表面改性的效果。试验结果表明 ,在相同的条件下 ,与平板 平板电极介质阻挡放电相比较 ,多针 平板电极介质阻挡放电具有较大的放电功率 ,能够对表面形状复杂的材料进行处理 ,且放电空间内更难产生细丝 ;用这种放电对聚四氟乙烯进行表面改性 ,能在较短的时间内获得与平板 平板电极介质阻挡放电相同的效果。

大气压微波放电CO_(2)等离子体温度的发射光谱诊断

大气压微波等离子体因具有活性粒子密度高、气体温度高、能量转换效率高、可控性好等独特优势,在分解和转化二氧化碳治理环境领域展现出重要的应用价值。以大气压微波等离子体的二氧化碳分解与转化为应用背景,开展了大气压微波等离子体的放电特性与温度参数的测量和诊断研究。通过研究等离子体炬的放电形态的变化规律,分析了大气压二氧化碳等离子体的放电特点;利用发射光谱的诊断方法,分析了二氧化碳放电区内产生的C_(2)分子的转动温度,得到了二氧化碳等离子体内不同位置在不同功率和不同气体流量下的放电形态以及温度的变化规律。研究结果表明,这种大气压微波等离子体的放电形态呈现明亮的中心放电区和外围的余辉区,且这两个区域存在清晰的边界;放电区的长度随微波功率增加接近线性增长,受送气流量大小的影响微弱。等离子体发射光谱诊断结果显示,大气压微波等离子体放电过程中,主放电区中除了化学荧光连续谱外还存在很强的C_(2)分子的Swan谱带;基于这一谱带计算得到的主放电区等离子体温度约为6 000 K,且这一温度几乎不随功率和气流的变化;不同中心放电区位置,温度略有变化(±100 K)。

石英管对平行WR-430波导谐振腔电场的影响(英文)

详细讨论了石英管对平行WR-430波导谐振腔内部电场强度的影响。在没有石英管时,电场强度在每个狭缝附近发生突变,其峰值沿着一个波导逐渐减小,而沿着另外一个波导逐渐增大。存在石英管时,内部电场变弱且沿着石英管内表面无规则振荡,而且电场沿着两个波导之间的中心轴线波动。当石英管壁厚度和离上下波导的距离分别为5和2mm时,谐振腔内部的平均电场强度达到最大,而且电场强区面积较大。当上述两者分别超过5和2mm时,内部电场的最大值会随着石英管壁厚度和距离逐渐减弱。低气压和大气压空气等离子体在谐振腔内部被激发,其形态比较接近各自的仿真的电场强度分布。

大型低温常压液氨储罐及配套冰机的设计选型

简述了当前大型低温常压液氨储罐的技术方案,比较了不同低温常压液氨储存方式的技术特点,同时对液氨储罐在不同的操作工况下配套冰机制冷能力给出了详细的计算方法,分析了影响冰机制冷量的各种因素,采用理论计算结合工程经验角度分析了影响冰机设计选型的各种要素,为大型液氨储存工艺方案选择及优化,各种氨储存系统操作工况下的冰机的配置、设计选型提供了借鉴和参考。

间冷循环燃气轮机低压工作线及影响因素分析

为详细掌握间冷循环燃气轮机的工作特性及实际运行过程中低压工作线的变动,考虑空气系统引气、压气机出口漏气对流量连续的影响,引入压气机与涡轮及相邻涡轮间的流量比例系数,理论推导间冷循环燃气轮机低压工作线方程,得到影响低压工作线的典型因素。开展间冷循环燃气轮机低压工作线在典型影响因素下的变动机理分析,不同于高压工作线变动分析采用等换算转速条件,低压工作线变动分析采用等高压转子增压比条件更为合理。依据间冷循环燃气轮机长期运行后典型影响因素的变化,获得间冷循环燃气轮机低压工作线的具体变动结果,即高压压气机效率降低、高压涡轮效率降低、高压涡轮导向器面积增加、间冷器性能衰减及二次水温度升高等会导致低压工作线升高,低压压气机效率降低、低压涡轮效率降低、低压涡轮导向器面积增加、低压出口漏气量增加及大气温度增加等会导致低压工作线降低。